Genes & Cells

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DOUBLING UP A normal female mouse embryo (left) has only female reproductive tissue, called the Müllerian duct (pink). Removing a protein called COUP-TFII causes a female mouse embryo (right) to develop both the female duct and male tissue called the Wolffian duct (blue).

Yao Laboratory/NIEHS

TICK TIMES TWO It can be difficult to correctly diagnose tick-borne diseases in locales with both the black-legged tick (left), which spreads Lyme disease, and the lone star tick (right), which can transmit southern tick‒associated rash illness or STARI.

Scott Bauer/USDA; CDC

WOUND UP Archaea microbes wrap their DNA (represented in yellow) around proteins called histones (purple) akin to the way plants and animals do.